Heterojunction Configuration Research Articles

Optimizing optoelectronics performance: theoretical and experimental study on ZnO thin film for Al/ZnO/p-Si photodiode

Abstract In this paper, a ZnO photodiode in a p-n heterojunction configuration is fabricated on a p-type Si substrate focusing specifically on ZnO/p-Si heterojunction photosensitive devices and photodiodes (PDs) using Al contacts. Through an experimental and theoretical analysis approach aims to evaluate the effects of important parameters, including ZnO layer thickness, defect density, and contact materials, on PD’s efficiency. Numerical analysis simulations comparatively examine the experimentally fabricated device performance at a 5 nm ZnO layer thickness by balancing photon absorption and carrier formation while minimizing carrier transport limitations. Experimentally process, an Atomic Layer Deposition (ALD) system was used to grow ZnO interlayers on one side of the polished Si wafer. Then, Al metallic contacts were created on the ZnO layers using a hole array mask. The PDs were then subjected to electrical characterization using I-V and I-t measurements under various illumination densities. Al/ZnO/p-Si PD’s device with active performance has been produced and analyzed with electrical parameters such as barrier height, photocurrent, spectral response, ideality factor and EQE were derived, analyzed and studied. In conclusion, this work provides a comprehensive understanding of the performance of Al/ZnO/p-Si PD at varying illumination intensities and offering a detailed analysis of key parameters influencing device efficiency for future optoelectronics applications.

Construction of metal-free dual S-scheme heterojunction photocatalysts by rational band alignment for efficient hydrogen evolution

Designing ternary heterojunction photocatalysts is regarded as a compelling approach to attain exceptional photocatalytic activity. However, they always suffer from poor interfacial contact and unclear charge transfer pathways. Herein, a metal-free dual S-scheme heterojunction photocatalyst comprised of black phosphorus (BP), carbon nitride (CN), violet phosphorus (VP) was designed by electrostatic self-assembly. The non-metallic feature of the BPCNVP heterostructure facilitates to form strong interfacial contact by coordinating active P sites in VP and BP with N atoms in CN. Notably, a definite dual S-scheme heterojunction configuration is achieved by rational band alignment of VP and BP, respectively, which significantly boosts the driving force for charge separation. The BPCNVP heterostructure exhibited a hydrogen evolution rate of 1669μmol h-1g−1 with excellent stability, surpassing most reported metal-free photocatalysts. This work demonstrates that the design of dual S-scheme heterojunction by metal-free materials provides valuable insights into the intricate reaction mechanism of ternary heterojunction photocatalysts.

Toward Full‐Color Vision Restoration: Conjugated Polymers as Key Functional Materials in Artificial Retinal Prosthetics

AbstractFor the prosthetic retina, a device replacing dysfunctional cones and rods, with the ability to mimic the spectral response properties of these photoreceptors and provide electrical stimulation signals to activate residual visual pathways, can relay sufficient data to the brain for interpretation as color vision. Organic semiconductors including conjugated polymers with four different bandgaps providing wavelength‐specific electrical responses are ideal candidates for potential full‐color vision restoration. Here, conjugated polymer photocapacitor devices immersed in electrolyte are demonstrated to elicit a photovoltage measured by a Ag/AgCl electrode 100 microns from the device of ≈−40 mV for 15–39 µW mm−2 of incident light power density at three wavelengths: 405 nm for blue photoreceptor candidate material, 534 nm for green, 634 nm for red. Photoresponse is substantially improved by introducing polymer donor/acceptor molecules bulk heterojunctions. Devices with bulk heterojunction configurations achieved at least −70 mV for green candidates with the highest at −200 mV for red cone candidates. These findings highlight the potential for organic materials to bridge the gap toward natural vision restoration for retinal dystrophic conditions such as age‐related macular degeneration, Stargardt disease, or retinitis pigmentosa and contribute to the ongoing advancements in visual prosthetic devices.

Comparative study on photocatalytic activity: Ni ferrite/Mg ferrite vs. Z-scheme Ni ferrite/silver/Mg ferrite heterojunction under solar radiation

This study investigates the photodegradation efficiency of core/shell structures comprising NiFe2O4/MgFe2O4 (NiF/MgF) and Z-scheme NiFe2O4/Ag/MgFe2O4 (NiF/Ag/MgF) heterojunctions for Methylene Blue dye degradation. In this study, solar radiation was used as a source of excitation. X-ray diffraction analysis reveals an increase in particle size and micro-strain for NiF/MgF and NiF/Ag/MgF, confirming the formation of core/shell structures. The NiF/Ag/MgF sample exhibits the highest magnetization, attributed to the RKKY magnetic interaction between NiF and MgF moments via the conduction electron of the Ag metal layer. Optical measurements indicate increased absorption coefficient and absorption bandwidth for core–shell structures. Photocatalytic activity measurements demonstrate that while bare MgFe2O4 MgF shows limited photodegradation efficiency, NiF/MgF and NiF/Ag/MgF heterojunctions significantly enhance photodegradation. The presence of the Ag metal layer in the NiF/Ag/MgF heterojunction reduces electron-hole pair recombination and enhances their separation, leading to exceptional photodegradation efficiency. These results highlight the significance of Z-scheme heterojunction configurations in augmenting photodegradation processes under solar radiation, offering notable economic advantages. Additionally, the high magnetization observed in the studied samples presents an opportunity for efficient waste material retrieval using a simple magnetic extraction method.

Self-powered photodetector based on 1D TiO2-3D CdS mixed dimensional heterostructure fabricated at low temperature

Solution processed photodetectors have garnered great attention in applications such as, machine vision perception, neuromorphic computing and opto-electronic memory storage. Though, such photodetectors offer several advantages such as ease of fabrication, high scalability, low thermal budget and low-cost processing, multi-modal functionality etc. however, they suffer from the major drawback of inferior device performance −as low responsivity and slow rise time, particularly due to the intrinsic poor crystallinity of the photoactive material. In this work, we demonstrate a solution processed photodetector with impressive performance at comparatively low processing temperatures (<150 °C) based on the mixed dimensional heterostructure configuration of 1D TiO2 nanorods and 3D CdS nanoflowers. TiO2 nanorods have been synthesized by hydrothermal technique, whereas their CdS sensitization is done by chemical bath deposition. Low cost carbon paste is used as electrode instead of conventional non-economic noble metal electrodes. X-ray diffraction studies validated excellent crystallinity of the photoactive material even under low temperature processing condition. The type-II Heterojunction (TiO2 and CdS) configuration photodetector shows efficient response at zero bias, thus yielding a self-powered device. The detector shows response in UV and visible region, with excellent responsivity of 110 mA/W (5 V), 563 µA/W (0 V) and a quicker rise time of 81 ms. Albeit the simple fabrication scheme and low processing temperatures, the detector exhibited promising figures-of-merit, which aids in fabrication of novel solution processed photodetectors.

Comparison of p-n and p-i-n vertical diodes based on p-PMItz/n-Si, p-PMItz/n-4HSiC and p-PMItz/i-SiO2/n-Si heterojunctions

In this paper, we present a comprehensive comparison study between p-n and p-i-n vertical diodes employing diverse heterojunction configurations under dark conditions. The diodes are fabricated utilizing p-PMItz as the organic semiconductor layer interfacing with different inorganic substrates, including n-Si (n-type silicon), n-4HSiC (n-type 4H silicon carbide), and incorporating an intrinsic SiO2 (silicon dioxide) layer in the p-PMItz/i-SiO2/n++-Si configuration. The current–voltage and dielectric characteristics are analyzed to discern the performance discrepancies among these diode configurations. The influence of heterojunction interfaces and band alignments on device behavior is investigated, shedding light on the charge transport mechanisms within these structures. Our findings reveal distinct trends in device characteristics for p-n and p-i-n diodes, highlighting the significance of heterojunction design in optimizing device performance. This comparative analysis offers valuable insights for the development of efficient organic–inorganic hybrid diodes tailored for various optoelectronic applications.

Electronic properties of c-BN/diamond heterostructures for high-frequency high-power applications

Using first principles calculations, this work investigates the suitability of diamond/c-BN heterojunctions for high frequency, high power device applications. The key quantities of band offsets and interface charge polarization are examined for different crystallographic orientations [(110), (111), or (100)], bond terminations (CB or CN), and substrates (diamond or c-BN). The results indicate that both the (111) and (100) structures with polar interfaces are likely to be a type-I alignment with the diamond conduction and valence band extrema nested within the c-BN bandgap, whereas the non-polar (110) counterpart may form type II as the valence band of c-BN is shifted down substantially lower. The valence band offsets are estimated to be around 0.2–0.55 eV and 1.2–1.3 eV for types I and II, respectively, with only a modest dependence on the order of layer stacking and bond termination. The (111) and (100) structures also show net charge polarization in a narrow region at the interface. The electron-deficient and electron-rich nature of the CB and CN bonding are found to induce charge redistribution leading to an essentially 2D sheet of negative and positive polarization, respectively, with a density on the order of 1012−1013q/cm2 (q=1.6×10−19 C). With the predicted band alignments suitable for carrier confinement as well as the possibility of the modulation and polarization doping, the diamond/c-BN heterostructures are a promising candidate for high-performance electronic devices with a highly conductive 2D channel. Both p-type and n-type devices appear possible with a judicious choice of the heterojunction configuration.

Design of novel solar-light-induced KBi6O9I/Ag–AgVO3 nanophotocatalyst with Ag-bridged Z-scheme charge carriers separation and boosted photo-elimination of hospital effluents

In this research, a novel solar-light-induced KBi6O9I/Ag–AgVO3 nanophotocatalyst with an Ag-bridged Z-scheme structure has been designed and synthesized through a sonochemical method to photo-degrade antibiotic hospital contaminants under simulated solar-light irradiation. Synthesized nanophotocatalysts with varying KBi6O9I to Ag–AgVO3 weight ratios underwent N2 Adsorption-Desorption, XRD, TEM, UV–Vis DRS, FESEM and PL analyses. The Ag-bridged Z-scheme-structured KBi6O9I/Ag–AgVO3 (1:1) nanophotocatalyst, demonstrated broad light absorption within the solar-light spectrum and showcased effective photocatalytic efficacy in degrading tetracycline antibiotic (88.3% and 83.5% removal for 25 and 50 mg/L, respectively, after 120 min). This performance outperformed other composited photocatalysts, as well as pure Ag–AgVO3 and KBi6O9I photocatalysts. The enhanced degradation efficiency of the KBi6O9I/Ag–AgVO3 (1:1) composite can be ascribed to the synergistic interaction of various elements. These include the surface plasmon resonance impact of silver nanoparticles, their pronounced sensitivity to solar irradiation, and the Z-scheme heterojunction configuration. Collectively, these factors work together to minimize the recombination rate of photoinduced electron-hole pairs, thereby amplifying the efficacy of photodegradation. Furthermore, the KBi6O9I/Ag–AgVO3 (1:1) composite photocatalyst displayed sustained pollutants elimination performance even after undergoing four consecutive cycles.

Self-powered dual-mode UV detector based on GaN/(BA)&lt;sub&gt;2&lt;/sub&gt;PbI&lt;sub&gt;4&lt;/sub&gt; heterojunction

As an important part of an intelligent photoelectric system, ultraviolet detector has been widely used in many fields in recent years. The research on self-powered heterojunction photodiode is particularly important. In this work, a dual-mode self-powered GaN/(BA)&lt;sub&gt;2&lt;/sub&gt;PbI&lt;sub&gt;4&lt;/sub&gt; heterojunction ultraviolet photodiode is prepared and discussed. The GaN film is deposited on sapphire by metal-organic chemical vapor deposition, and then the (BA)&lt;sub&gt;2&lt;/sub&gt;PbI&lt;sub&gt;4&lt;/sub&gt; film is spin-coated onto the surface of the GaN film to construct a planar heterojunction detector. The X-ray diffraction, energy-dispersive X-ray spectroscopy mapping and scanning electron microscope measurements are used to determine the quality of GaN and (BA)&lt;sub&gt;2&lt;/sub&gt;PbI&lt;sub&gt;4&lt;/sub&gt; thin films. When the film is illuminated by 365 nm light with a power density of 421 μW/cm&lt;sup&gt;2&lt;/sup&gt; at 5 V bias, the responsiveness (&lt;i&gt;R&lt;/i&gt;) and external quantum efficiency (EQE) are 60 mA/W and 20%, respectively. In self-powered mode, the rise time (&lt;i&gt;τ&lt;/i&gt;&lt;sub&gt;r&lt;/sub&gt;) and decay time (&lt;i&gt;τ&lt;/i&gt;&lt;sub&gt;d&lt;/sub&gt;) are 0.12 s and 0.13 s, respectively, illustrating the fast photogeneration process and recombination process for photo-excited electron-hole pairs. And, the &lt;i&gt;R&lt;/i&gt; is 1.96×10&lt;sup&gt;–4&lt;/sup&gt; mA/W, owing to the development of space charge region across the interface of GaN thin film and (BA)&lt;sub&gt;2&lt;/sub&gt;PbI&lt;sub&gt;4&lt;/sub&gt; thin film. The outcomes of this study unequivocally demonstrate the extensive potential and wide-ranging applicability of self-powered UV photodiodes based on the GaN/(BA)&lt;sub&gt;2&lt;/sub&gt;PbI&lt;sub&gt;4&lt;/sub&gt; heterojunction configuration. Moreover, this research presents a new concept that provides a novel avenue to the ongoing development of intelligent optoelectronic systems.

Performance of UV photodetector of mechanical exfoliation prepared PEDOT:PSS/&lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; microsheet heterojunction

&lt;sec&gt;Ultrawide-bandgap (4.9 eV) &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; material possesses exceptional properties such as a high critical-breakdown field (~8 MV/cm) and robust chemical and thermal stability. However, due to the challenges in the growth of p-type &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt;, the preparation of homojunction devices is difficult. Therefore, the utilization of heterojunctions based on &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; provides a viable approach for fabricating ultraviolet photodetectors. Poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT:PSS), a p-type organic polymer material, exhibits high transparency in a 250–700 nm wavelength range. Additionally, its remarkable conductivity (&gt;1000 S/cm), high hole mobility (1.7 cm&lt;sup&gt;2&lt;/sup&gt;·V&lt;sup&gt;–1&lt;/sup&gt;·s&lt;sup&gt;–1&lt;/sup&gt;), and excellent chemical stability make it an outstanding candidate for serving as a hole transport layer. Consequently, the combination of p-type PEDOT:PSS with n-type &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; in a heterojunction configuration provides a promising way for developing PN junction optoelectronic devices.&lt;/sec&gt;&lt;sec&gt;In this study, a &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; microsheet with dimensions: 4 mm in length, 500 μm in width, and 57 μm in thickness, is successfully exfoliated from a &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; single crystal substrate by using a mechanical exfoliation technique. Subsequently, a PEDOT:PSS/&lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; organic/inorganic p-n heterojunction UV photodetector is fabricated by depositing the PEDOT:PSS organic material onto a side of the &lt;i&gt;β&lt;/i&gt;-Ga&lt;sub&gt;2&lt;/sub&gt;O&lt;sub&gt;3&lt;/sub&gt; microsheet. The obtained device exhibits typical rectification characteristics, sensitivity to 254 nm ultraviolet light, and impressive self-powering performance. Furthermore, the heterojunction photodetector demonstrates exceptional photosensitive properties, achieving a responsivity of 7.13 A/W and an external quantum efficiency of 3484% under 254 nm UV light illumination (16 μW/cm&lt;sup&gt;2&lt;/sup&gt;) at 0 V. Additionally, the device exhibits a rapid photoresponse time of 0.25 s/0.20 s and maintains good stability and repeatability over time. Notably, after a three-month duration, the photodetection performance for 254 nm UV light detection remained unchanged, without any significant degradation. This in-depth research provides a novel perspective and theoretical foundation for developing innovative UV detectors and paving the way for future advancements in the field of optoelectronics.&lt;/sec&gt;

A g-C3N4/rGO/Cs3Bi2Br9 mediated Z-scheme heterojunction for enhanced photocatalytic CO2 reduction.

Photocatalytic CO2 reduction plays a crucial role in advancing solar fuels, and enhancing the efficiency of the chosen photocatalysts is essential for sustainable energy production. This study demonstrates advancements in the performance of g-C3N4 as a photocatalyst achieved through surface modifications such as exfoliation to increase surface area and surface oxidation for improved charge separation. We also introduce reduced graphene oxide (rGO) in various ratios to both bulk and exfoliated g-C3N4, which effectively mitigates charge recombination and establishes an optimal ratio for enhanced efficiency. g-C3N4/rGO serves to fabricate a hybrid organic/inorganic heterojunction with Cs3Bi2Br9, resulting in a g-C3N4/rGO/Cs3Bi2Br9 composite. This leads to a remarkable increase in photocatalytic conversion of CO2 and H2O to CO, H2 and CH4 at rates of 54.3 (±2.0) μmole- g-1 h-1, surpassing that of pure Cs3Bi2Br9 (11.2 ± 0.4 μmole- g-1 h-1) and bulk g-C3N4 (5.5 ± 0.5 μmole- g-1 h-1). The experimentally determined energy diagram indicates that rGO acts as a solid redox mediator between g-C3N4 and Cs3Bi2Br9 in a Z-scheme heterojunction configuration, ensuring that the semiconductor (Cs3Bi2Br9) with the shallowest conduction band drives the reduction and the one with the deepest valence band (g-C3N4) drives the oxidation. The successful formation of this high-performance heterojunction underscores the potential of the developed composite as a photocatalyst for CO2 reduction, offering promising prospects for advancing the field of solar fuels and achieving sustainable energy goals.

Construction of hierarchical In2O3/In2S3-ZnCdS ternary microsphere heterostructures for efficient photocatalytic nitrogen fixation.

Photocatalytic ammonia production holds immense promise as an environmentally sustainable approach to nitrogen fixation. In this study, In2O3/In2S3-ZnCdS ternary heterostructures were successfully constructed through an innovative in situ anion exchange process, coupled with a low-temperature hydrothermal method for ZnCdS (ZCS) incorporation. The resulting In2O3/In2S3-ZCS photocatalyst was proved to be highly efficient in converting N2 to NH3 under mild conditions, eliminating the need for sacrificial agents or precious metal catalysts. Notably, the NH4+ yield of In2O3/In2S3-0.5ZCS reached a significant level of 71.2 μmol g-1 h-1, which was 10.47 times higher than that of In2O3 (6.8 μmol g-1 h-1) and 3.22 times higher than that of In2O3/In2S3 (22.1 μmol g-1 h-1). This outstanding performance can be attributed to the ternary heterojunction configuration, which significantly extends the lifetime of photogenerated carriers and enhances the spatial separation of electrons and holes. The synergistic interplay between CdZnS, In2S3, and In2O3 in the heterojunction facilitates electron transport, thereby boosting the rate of the photocatalytic nitrogen fixation reaction. Our study not only validates the efficacy of ternary heterojunctions in photocatalytic nitrogen fixation but also offers valuable insights for the design and construction of such catalysts for future applications.

Interface Analysis of CuO/ZnO Heterojunction for Optoelectronic Applications: An Experimental and Simulation Study

Material interfaces are essential building blocks for a wide variety of emerging technologies. Well‐defined and optimized heterostructures serve as the foundation for developing materials toward innovative optoelectronic applications. The distinctive features of heterojunctions have recently attracted the attention of the optoelectronics community, prompting a rise in the construction of modern devices. A solution‐based method is presented for developing a heterojunction made of copper oxide nanorods coated with zinc oxide thin films. Coating ZnO thin films on vertically oriented CuO nanorods results in the development of ZnO/CuO heterojunction configuration, which exhibits outstanding optoelectronic capabilities like broadband absorption and white light emission. Additionally, systematic ab initio computations have been done to comprehend the impact on various optical and electrical properties. It is observed that defects play a very crucial role in determining the quantum efficiency as well as improved visible to near‐infrared absorption. Moreover, the formation of energy levels near conduction bands in the presence of vacancies leads to broad absorption in the ultraviolet–visible region, and therefore, greater than 60% quantum efficiency over the range 350–800 nm is observed. Therefore, the presented work serves as the foundation for additional design and optimization techniques for oxide heterojunctions and emerging applications.

Bulk Heterojunction Antimony Selenosulfide Thin‐Film Solar Cells with Efficient Charge Extraction and Suppressed Recombination

AbstractAs an emerging earth‐abundant light harvesting material, antimony selenosulfide (Sb2(S,Se)3) has received tremendous attention for photovoltaics. Manipulating the carrier separation and recombination processes is critical to achieve high device efficiency. Compared to the conventional planar heterojunction (PHJ), the bulk heterojunction (BHJ) configuration affords great potential to enable efficient charge extraction. In this work, BHJ Sb2(S,Se)3 solar cells are constructed based on CdS nanorod arrays (NRAs). Highly ordered CdS NRAs with appropriate nanorod lengths and diameters are obtained by regulating the growth environment and screening different substrates for CdS deposition. A low‐temperature oxygen doping strategy implemented on CdS NRAs is further developed to improve the optoelectronic and defect properties as well as form a favorable cascade band structure for CdS NRAs, so as to realize more efficient charge extraction and suppressed recombination at the heterointerface. As a result, the CdS NRAs‐based superstrated BHJ Sb2(S,Se)3 solar cell yields a considerable power conversion efficiency of 8.04%, outperforming that of the PHJ device. A careful comparative study of PHJ and BHJ based on electrostatic field simulations indicates that the BHJ allows more efficient charge extraction and transport. This work highlights the great potential of BHJ configuration for constructing high‐performance antimony chalcogenide solar cells.

Anisotropic frictional characteristics among MoS2/SiO2 layer-dependent heterojunctions

The findings pertaining to the two-dimensional single-layer interface of MoS2 and SiO2 reveal that the matched heterostructure exhibits a prominent frictional anisotropy with a hexagonal six-fold symmetry. Notably, the misaligned and aligned contacts exhibit distinct frictional coefficients of 0.074 and 0.059, respectively. Moreover, as the number of layers increases, the features of frictional anisotropy decline considerably until reaching nine layers. The adaptive nanodevices derived from this research may hold significant potential for application in various heterojunction configurations.

Suppressing Bimolecular Charge Recombination and Energetic Disorder with Planar Heterojunction Active Layer Enables 18.1% Efficiency Binary Organic Solar Cells

The performance of organic solar cells has been dramatically enhanced due to the use of bulk heterojunction active layer structure. However, blending donor and acceptor in the bulk volume results in a large extent of bimolecular charge recombination and increasing energetic disorder. Herein, we fabricated organic solar cells with polymer donor PM6 and nonfullerene acceptor N3 in bilayer structure to investigate the impact of planar heterojunction configurations on charge recombination and energetic landscapes. We find superior crystallinity features in the bilayer composed of pure donor and acceptor layers. The bimolecular charge recombination and energetic disorder are effectively suppressed compared with the bulk heterojunction counterparts. Thus, a power conversion efficiency as high as 18.1% (17.8% averaged) is achieved, which stands among the top values of planar heterojunction organic solar cells. In addition, improved device shelf stability is observed because of the fewer donor–acceptor interfaces in the active layer. Our results suggest that a planar heterojunction structure could efficiently suppress the bimolecular charge recombination and energetic disorder, providing an alternative pathway for developing solution-processed organic solar cells.

ZnO/Pt/P3HT Hetero-Junction Configuration for High Performance Self-Biased UV Detection

In this work, a self-biased hybrid UV photodiode has been developed by introducing Pt nanoparticles at ZnO/P3HT interface which has increased barrier potential at the interface, thus significantly improving various device parameters such as ideality factor, selectivity, and rectification ratio and reduced the dark current by ~1 order. Further, the photosensitivity, photoresponsivity, and specific detectivity of the device in the self-biased mode were 46, 14.8 mA/W, and 1.2×10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">12</sup> Jones, respectively. Moreover, the response time of the device was shortened to 45 ms. Thus, the reported device has the potential to fulfill the demands of modern technologies where fast response speed and high UV photosensitivity, and low power consumption are prime requirements.

Cu2O/UiO-66-NH2 composite photocatalysts for efficient hydrogen production from ammonia borane hydrolysis

Ammonia borane (NH3BH3, AB) is a chemical hydride with a high hydrogen capacity of 19.6 wt%, which makes it a promising hydrogen carrier. Cuprous oxide (Cu2O) is one of the most active photocatalysts for AB dehydrogenation at ambient conditions. However, the instability due to photocorrosion and high charge recombination are the main drawbacks of practical application. In this work, Cu2O is coupled with a metal-organic framework (MOF) as a composite photocatalyst (Cu2O/UiO-66-NH2), which demonstrates a better photocatalytic performance in AB hydrolysis than its pure counterpart samples because of the heterojunction configuration. The Z-scheme charge transfer pathway in Cu2O/UiO-66-NH2 composite can improve charge separation, hydrogen production efficiency, photocatalyst stability, and reduce activation energy. The optimum composite photocatalyst comprising 50 wt% Cu2O loading shows the highest hydrogen evolution yield of almost 2.3 equivalent H2 from AB hydrolysis.

Local charge distribution manipulation by oxyhydroxide heterojunction toward urea photoelectrolysis

Photoelectrochemical urea splitting can simultaneously produce hydrogen and remediate urea wastewater, which can also reduce the need for the electric energy consumption of urea electrolysis. However, the lack of an appropriate cocatalyst severely restricts the improvement of photoelectrochemical activity for urea splitting. Here, we synthesize Co/Ni oxyhydroxide cocatalysts with a heterojunction configuration on the surface of BiVO4 films. Due to the difference in Fermi energies, CoOOH and NiOOH catalysts serve as nucleophilic and electrophilic active sites, respectively. Thus, the carbonyl group and amino group of urea can adsorb on CoOOH and NiOOH through the bridging coordination, respectively. Meanwhile, the charge transfer across CoOOH/NiOOH heterointerface improves the oxidation state of Ni species in NiOOH. The heterojunction cocatalyst and high oxidation state of Ni species promote the adsorption and fracture of chemical groups in urea molecules. Thanks to the composite design of photoanode, under AM1.5G illumination, the composite photoanode exhibits a photocurrent density of 4.93 mA/cm2 at 1.23 VRHE under neutral conditions, which is the highest value achieved with BiVO4. The onset potential of the composite photoanode shifts negatively by 140 mV. This work demonstrates that the fabrication of heterojunction cocatalysts is an effective strategy toward urea photoelectrolysis.

UV-Visible photovoltaic detector based on biomaterial-inorganic semiconductor in the propolis/n-Si heterojunction configuration

Here, we will demonstrate that propolis can be used in photodetectors in self-powered mode, long-term stable and high performance by coating on n-Si with spin coating. The surface morphology of the propolis was studied by SEM-EDX and XRD analyses and elemental analysis was investigated by ICP-MS spectroscopy. The propolis/n-Si photovoltaic detector showed excellent diode characteristics with a rectification ratio of 23815 for ± 2 V. It was seen that the propolis/n-Si photovoltaic detector exhibited self-powered mode. Maximum responsivities of 0.113 A/W in the UV wavelength of 365 nm, and 0.018 A/W in the visible light intensity of 150 mW/cm2 were achieved. The maximum detectivities were 4.04 × 109 Jones at the UV light of 365 nm and 4.17 × 108 Jones visible light. It is expected that the self-powered propolis/n-Si photovoltaic detector will have potential application in future optoelectronic devices.